![]() ![]() Just like a screen, when galaxies are farther away, all those stars blend together, and the galaxy will look really smooth, similar to the way the pixels on a screen blend together when you sit back from it. When galaxies are close to us, we see bigger bumps coming from that galaxy due to how the galaxies stars are organized. ![]() Now a galaxy is not a phone screen but it does behave in a similar way. Similarly, galaxies are just a bunch of stars clumped together. You can make out pixels on your screen when it is close because your screen is just made up of a lot of pixels. Now, back away until you are no longer able to see the pixels. If the screen is really close to your face, you will be able to see the pixels, or the tiny lights that make up the image you see, on the screen. To explain how SBF works, take a close look at the phone or computer screen you are reading this on. But how do we even know how big space is? There are many different ways to measure things in space, but I focus on measuring distance to galaxies using a very special method called surface brightness fluctuations (SBF). It is pretty cool that space is so huge, or at least I think so. I like parsecs because, for me, they are easier to use and understand compared with all the zeros there are when we use kilometers. Remember Alpha Centauri, the closest star? It is 1.347 parsecs, or 41,560,000,000,000 (or 41.56 trillion) kilometers away. Instead, we use a measurement that we call a parsec. Measuring Space With Parsecsīecause space is so big, many astronomers do not like to say how far away things are using miles or kilometers. To get there, it would be like driving to the sun almost 300,000 times! The closest galaxy, Andromeda, is nearly 600,000 times farther than Alpha Centauri! The farthest galaxies I measure are over 100 times farther than Andromeda, and to get to the end of the visible universe, you have to go almost 150 times farther than that! 1 Anyway, if you wanted to drive to the end of the visible universe, or pretty much anywhere out in space, it would take a really long time. It would take nearly 4,000 times longer to get to the sun than to drive around the earth! That is ~22,000 days in the Ferrari! The closest star that is not the sun is called Alpha Centauri. Now imagine if your Ferrari suddenly could travel to the sun. If you did not have to stop, you could go around the earth in about 133 h, or 5 and a half days. You are in a Ferrari, zooming at 300 kph (186 mph). Pretend you are on the Autobahn in Germany. He was not kidding either! Imagine it this way. Space is really big! You just would not believe how vastly hugely mindbogglingly big it is. In his book, The Hitchhikers Guide to the Galaxy, Douglas Adams says, “Space is big. Most galaxies measured in this way are millions of light years away. Astronomers can use what are called surface brightness fluctuations (SBF, for short), along with the color of a galaxy, to calculate how far away it is from earth. Measuring distances to other galaxies is an important part of our ability to understand how the universe works. ![]()
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